Correlation between rheology of superplasticized fresh mortars and fresh concretes

The examination of superplasticizer compatibility with cement and its influence on rheology of concrete has essential significance from the workability control point of view. Usually, the performance of superplasticizer is tested using cement paste. However, the effects of superplasticizer on rheological properties of cement paste and concrete may be considerably different depending on the material in use. Simultaneously analysis of so far executed studies indicate that mortar can be considered to be concrete without coarse aggregate and its testing has attractions for the study of superplasticizer and other ingredients effects at small scale. The main objectives of this study were to investigate the influence of superplasticizer on rheology of mortar and of concrete and to develop empirical formula making possible of forecasting rheological properties of concrete basing on rheological measurements made on mortars. The influence of superplasticizer type and content on rheology of mortars and concretes that have different mortar volumes was investigated, cement type and w/c influence was also considered. Rheology results have been evaluated according to the Bingham model. Rheological parameters were measured using BT2 rheometer. The results show that superplasticizer has generally similar influence on the rheological parameters of mortar and concrete. It was demonstrated, that superplasticizer effect on rheological properties of concrete could be predicted with a high degree of certainty from on rheological measurements made on mortars. The regression models of influence of rheological parameters of mortars on rheological parameters of fresh concretes made of different volumes of analogical mortars were developed. These models may be applied for designing and developing workability of concrete.